Below is the formula I found doing a search on the forum. It is from 2005 and I took it to the Sherwin Williams shop and they said Violet is not a pigment that they use:

Sherwin Williams pigments and using a Martin Senour "Bright Life" Latex Eggshell Enamel, Neutral Base (Qt.):
Black: 22/32
Blue: 1 oz + 16/32
Violet: 16/32
Red Oxide: 1/64
White: 21/32
Does anyone have a revised formula for JBL blue? I'm repainting a pair of 4301B's.